CVE-2021-40084: opensysusers through 0.6 does not safely use eval on files in sysusers.d that may contain shell metacharacters

Q: How do I fix CVE-2021-40084?

opensysusers: upgrade to newer than 0.6. Exact commands for each OS are on this page.

Q: Is CVE-2021-40084 being exploited?

CVE-2021-40084 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-40084 affect?

CVE-2021-40084 affects opensysusers. Severity is critical (CVSS 9.8). opensysusers through 0.6 does not safely use eval on files in sysusers.d that may contain shell metacharacters. For example, it allows command execution via a crafted GECOS field whereas systemd-sysusers (a program with the same specificati

Q: How urgent is CVE-2021-40084?

Priority 71/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

This week

CRITICAL 9.8REMOTEWATCHLISTUPGRADE

CVE-2021-40084 is a critical-severity flaw (CVSS 9.8) affecting opensysusers. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

opensysusers through 0.6 does not safely use eval on files in sysusers.d that may contain shell metacharacters. For example, it allows command execution via a crafted GECOS field whereas systemd-sysusers (a program with the same specification) does not do that.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.9% (top 13%)
CISA exploited list	No
Weakness	CWE-94
Published	2021-08-25
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: artixlinux

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-08-25 01:15 UTCPublished CVE record published
2026-06-17 04:06 UTCUpdated Record last modified

artixlinux opensysusers UPGRADE

Affected: <= 0.6

Fixed in: newer than 0.6

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy opensysusers || rpm -q opensysusers || opensysusers --version

2. UPGRADE to newer than 0.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade opensysusers

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade opensysusers

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-40084?

opensysusers: upgrade to newer than 0.6. Exact commands for each OS are on this page.

Is CVE-2021-40084 being exploited?

CVE-2021-40084 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-40084 affect?

CVE-2021-40084 affects opensysusers. Severity is critical (CVSS 9.8). opensysusers through 0.6 does not safely use eval on files in sysusers.d that may contain shell metacharacters. For example, it allows command execution via a crafted GECOS field whereas systemd-sysusers (a program with the same specificati

How urgent is CVE-2021-40084?

Priority 71/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

References

← Back to latest CVEs